1. Field of the Invention
The invention is related to electrically actuated valves and in particular to an electrically actuated pneumatic proportional valve having an output pressure proportional to the pulse width of the individual pulses in a received pulse train signal.
2. Prior Art
Electrically actuated or solenoid valves are well known in the art. These values, for the most part operate in an on-off mode and can be made to operate in proportional mode by actuating them with a pulse train signal in which the fluid delivery is a function of the ratio between the on and off times of the valve. These types of valves work well where the quantity of fluid is relatively small, but as quantity of delivered fluid increases, the solenoids necessarily become larger and require more electrical power for actuation. In addition, with the increase in the size of the valves, their reaction time becomes much slower, making it difficult to integrate or filter out the individual pressure pulses due to the opening and closing of the valve. Therefore the fluid flow or fluid pressure at the outlet of devalve will vary with the frequency at which the valve is actuated. As a result, the actuator responsive to the output of the valve will not operate smoothly, but will fluctuate at the operating frequency of the valve.
Another problem with the on-off type valves is that the fluid pressure at the outlet of the valve will vary with the fluid consumption rate of the actuator, and are not well suited for the type of actuator which responds primarily to the fluid pressure and not the quantity of fluid flow.
The present invention is a high volume electrically actuated proportional valve which overcomes the problems encounted in the prior art.